Support for underwater pipe lines

ABSTRACT

This invention relates to a stiffener assembly for controlling the bend of a pipe or pipe bundle in areas where large bending moments are expected. A plurality of stiffeners are secured along the length of pipe in an end-to-end relationship and in such a manner as to allow the pipe to deflect to a point where the bending stress is still below its yield point.

United States Patent [72] inventors Walter Brown Long Beach, Calif.;Donald E. Smith, Nashville, Tenn. 21 Appl. No. 1.493 [22} Filed Jan.8,1970 (45] Patented July 6,1971 [73] Assignee North American RockwellCorporation [54] SUPPORT FOR UNDERWATER PIPE LlNES l l C laims, 10Drawing Figs.

[52] U.S.Cl 138/106, 138/172, 52/693 [51] lnt.C1 F161 3/02 {50]FieldolSearch 138/172, 106, 107; 52/693, 646

[56] References Cited UNITED STATES PATENTS 1,703,605 2/1929 Ballantyne138/106 Primary Examiner-Herbert F. Ross AtlorneysL, Lee Humphries andCharles F. Dischler ABSTRACT: This invention relates to a stiffenerassembly for controlling the bend of a pipe or pipe bundle in areaswhere large bending moments are expected. A plurality of stiffeners aresecured along the length of pipe in an end-to-end relationship and insuch a manner as to allow the pipe to deflect to a point where thebending stress is still below its yield point.

PATENTED JUL 6 IHYI SHEET 1 BF 3 INVENTORS. WALTf/P BROWN DONALD E.SMITH A T TORNE Y PATENTEDJUL 6|97I 3.590.878

SHEET 2 0F 3 INVENTORS. WALTER BROWN DONALD E. SMITH C WMQ FFALMATTORNEY PATENTEUJUL 6, 3.590.878

sum 3 [IF 3 fLQl INVISN'I'ORS. WALTER snow/v DONALD 5mm A T TORNf ySUPPORT FOR UNDERWATER PIPE LINES BACKGROUND OF THE INVENTION With theincrease in underwater activities in recent times, there have arisenmany problems in areas which did not exist heretofore. One of theimportant areas, as an example, is underwater oil or gas wells. Thereare three phases involved in underwater oil well operations. That is,first, drilling the well; second, completion of the well; and third,production of the well.

The phase that this invention is more concerned with is the third phase,wherein the well is capable of producing a flow of gas and/or oil withmaximum trouble free operation.

This invention relates to pipeline or pipe bundles that are needed asconduits between underwater vessels, pumping stations, wells or othertype of flow stations including riser manifolds.

It should be noted that this invention is particularly cncerned with oilwell operations where the depth of the ocean or sea floor is such thatdivers are unable to work.

When laying pipe on land it is customary to dig a ditch, the bottom ofwhich is smooth with only gradual changes of inclining or declininggrades for large transitional radii. In the case of ditches or valleysthat have to be crossed bridges or bridgelike devices are provided.Therefore, it can be understood that the pipe is supported over its fulllength and is not subjected to bending stresses.

However, when laying pipe in deep water, the above procedures are, foreconomical reasons, out of the question. The underwater geographicalconditions and terrain are somewhat unpredictable. The pipe may be lyingpartly in soft sand, mud, and/or bedrock and will have additionalproblems to overcome, such as sudden steps in terrain, sharp rockyridges or valleys which cannot easily be removed.

As an example, a pressure vessel is normally located on a base supportstructure above the ocean floor, but well below sea level. The basestructure is generally located at least 25 feet above the ocean floor.Therefore, any pipe connections, such as a flowline connector from apressure vessel or the like, will be at a substantial distance above theocean floor. A pipe connected to a unit under the above conditions willhave to bridge an unsupported distance without buckling or causing anunacceptable reduction of flow area. It is obvious that under theseconditions, the pipe or pipe bundle near the pressure vessel will besubjected to a high degree of bending moment between the base structureand the ocean floor.

A similar support requirement is also to be found near the crossing of aravine. Stiffener assemblies are, therefore, required in these areas toeliminate or control any positive or negative bending moments that wouldtend to occur due to the weight of the pipe being supported by unevenfeatures of the terrain at various specific points.

SUMMARY OF THE INVENTION This invention relates to stiffener assemblieswhich are required to be placed at points along pipe or pipe bundles,where insufficient support of the pipe can be expected rather thanpreparing the ocean or sea bottom for the support thereof. The controlof the bending moment of the pipe is necessary and is accomplished bysecuring stiffener assemblies in end-to-end relationship to each otherat specific points along the pipe.

Since the depth of the ocean in which the pipeline is to be laid is atsuch a depth that it is not possible for divers to work, a fathometerreading of the area is taken. The reading will then indicate therequired position of the stiffeners on the pipeline.

Collars are then located at the required locations along the pipe. Inthe case of pipe bundles (a group of different sized pipes strungtogether along their length) collars will be secured to the largest pipein .the bundle, in this specific case having a size of approximately 8inches.

After the collars are secured to the pipe, which is normallyaccomplished by welding, the pipe line is floated on the water andrequired size stiffeners are fastened around each equally spaced collar.When the stiffeners are secured in place, the pipe and stiffeners arelowered into position.

The stiffeners will start taking hold after the stiffest pipe in thebundle has started bending and before the bending stress reaches theyield point of the pipe.

The stiffeners themselves can be made of any suitable light materialhaving an open lightweight truss design so that flotation devices arenot required to support the pipe.

Each stiffener comprises a connecting saddle which is centrallypositioned on the upper portion of the stiffener assembly. The saddle islocated intermediate the ends of a nonlinear convexed support beam andis an integral part thereof. At each free end of the support beam thereis fixed a shoe member and each member is formed to receive the pipe forengagement therein when the pipe has a bending moment in the directionof the shoes. Positioned in opposing relationship to the shoes are endbraces which are fixed to the underside of the support beam and extendsubstantially perpendicularly thereto. A column is connected at itsrespective ends to the extended ends of each respective end brace andremote from the support beam. The alignment of each stiffener assemblyin a side-to-side relationship is accomplished by guide means attachedto one of said braces at the lower end thereof, for receiving theadjacent brace of an adjoining stiffener assembly. For greater supportof the support beam, a center brace is vertically positioned between thelower column and the support beam. In addition, a pair of diagonallysupporting trusses are included and are fixed at one end to the uppersupport beam, adjacent to the center bar, the opposite end of which isfixed to the lower column adjacent the lower end portions of the endbraces.

Therefore, it is an object of the invention to control the bend of pipeby use of a group of stiffener assemblies where known bending momentsare to occur when the pipe or pipe bundle is laid on the bottom of theocean floor.

A further object of the invention is to stiffen the pipe bundle or pipeat places where insufficient support can be expected rather than preparethe supporting sea bottom.

It is still a further object of the invention to limit the bend of astring of pipe before the bending stress reaches the yield point.

Other characteristics, advantages and objects of my invention can bemore readily appreciated from the following description and appendedclaims. When taken in conjunction with the accompanying drawings, thisdescription forms a part of the specification wherein like referencesand characters designate corresponding parts in several views which areas follows:

FIG. 1 is a diagrammatic illustration showing typical applications ofthe invention;

FIG. 2 is an elevational view of the invention secured to a string ofstraight pipe;

FIG. 3 is an elevational view of the invention secured to a string ofpipe being bent by a bending moment;

FIG. 4 is an enlarged cross section taken along line 4-4 of FIG. 2;

FIG. 5 is an enlarged cross section taken along line 5-5 of FIG. 2;

FIG. 6 is a cross section taken substantially along line 6-6 of FIG. 2showing a pipe bundle supported thereon;

FIG. 7 is a cross section taken along line 7-7 of FIG. 5;

FIG. 8 is a bottom plan view of the guide means;

FIG. 9 is a sectional view illustrating another method of positioning apipe line;

FIG. 10 is a sectional view taken along line 10-10 of FIG. 1 showing theinvention positioned on a pipe line bundle which is capable of having apositive or negative bending moment.

Referring now to the drawings, there is shown in the diagrammatic viewof FIG. 1 a schematic illustration of a group of stiffener structures,generally indicated by reference numeral 10, which are attached to theelongated element 12 along its length. The elongated element representseither a single or multitubular line of end-to-end welded pipes. Theabove view illustrates the many typical areas in which the applicationof stiffener structures can be used. As can be seen, there is a pressurevessel 14 which is located and supported by a base or platform structure16 just above the sea floor 17 but well below the water surface 18.Whenever a pipeline such as 12 is to be connected to a pressure vesselof one kind or another, there will be a flow connection as illustratedgenerally at 20. One free end of the pipeline 12 is connected to theflow connector 20 and then lowered therefrom to the sea floor 17,wherein the distance between the connection and the sea floor is suchthat a bending will occur in the pipeline which would cause damage inthe form of buckling or an unacceptable reduction in the area of thepipeline to cause a reduced flow of fluid therethrough. It is,therefore, necessary to support the pipe at this critical bending areaby the stiffeners 10.

It should be noted at this time that the above referred to multitubularline comprises a group of two or more pipelines, each of which generallyhas a different size diameter. These pipes are supported and tied to thelargest pipe of the group. This multitubular line will hereinafter bereferred to as a pipe bundle.

The stiffener assembly 10 comprises a rigid skeleton-type frameworkhaving a nonlinear convex support beam 22 which is positionedlongitudinally along the length of the pipe 12 at predetermined pointsalong the length thereof and substantially parallel thereto, as can bereadily seen in FIGS. 2 and 3 respectively. A securing means, generallyindicated as 23, for securing the support beams to the pipe is locatedintermediate the ends of said support beams. The securing means 23comprises a connecting means such as a pair of fastening straps 24,collar 25 and a saddle member 26 which cooperate together to establishthe location of each stiffener assembly in an end-toend relationship.Each collar 25 is selectively positioned along the pipe 12 and isattached thereto by welding or other suitable means. The collars areevenly spaced relative to each other and located in the area where thebending of the pipe will most likely occur. After the attachment of thecollars 25, each assembly structure is fitted to each collar by means ofthe saddle member 26, as can be seen in FIGS. 5 and 7, respectively.This is accomplished by a channel 27 in the concaved face portion 28 ofthe saddle member which engages with the collar 25. The concave faceportion 28 is curved to fit the outer curvature of the pipe 12. Eachstiffener structure 10 is then secured to the stringer 12 by thetie-down bands or straps 24 located on each side of collar 25. Thestraps 24 encircle the pipe 12 along with the saddle 26 and are securedthereto by welding each strap into place. The saddle member 26 iscentrally positioned on the support beam 22 as that of an apex havingdivergently angulated extending arm members. Said angulated members 22aand 22b, respectively, are an integral part of said saddle member andeach member, together as a unit, comprises the support beam 22. At eachfree end of each arm member, there is fixed a concave shoe or bracket30, which is adapted and formed to receive the outer curvature of pipe12 for engagement therein when said pipe has a bending in the directionof the shoe.

It can be seen in FIG. 2 that the pipe 12 does not have a bending momentat this particular point and the support beam 22, being angulateddownwardly and away from said pipe, creates a space between the convexsurface 31 of the shoe 30 and the lower portion of the pipe wall. Thisspace then becomes a working area wherein the pipe may move or bendunder stress but yet can be controlled so that the pipe may be stressedonly to a set point below the yield stress and thereby protect the pipefrom damage.

Referring now to-FIG. 3, there is illustrated a stringer which is shownbowed under stress by a bending moment occuring in pipe 12. Thecurvature of the pipe fits and is received into the convex surface 31 ofthe shoe at each end of the stiffener assembly.

All

Positioned below each shoe and integrally connected thereto are endbraces 32 which extend downwardly from said support beams andsubstantially perpendicularly thereto. Connected to each of therespective lower end portions of the end braces 32 is a horizontalcompression column member 34, which is substantially parallel to theaxis of the pipe 12 and is remotely located from the support beam 22 forgreater structural support. Intermediate the ends of the lower columnmember 34, and centrally mounted thereon, is a vertical center brace 36.The opposite end ofsaid center brace is joined to the support beam atthe apex thereof. That is, the upper end of the brace 36 becomes anintegral part of the saddle and support beam 22 as means to aid in thestructural support of the skeleton-type framework. In addition, a pairof diagonally supporting truss members 38 are arranged so that one endof each truss is fixed to the column member 34 adjacent to the lower endof each end brace, and the opposite ends are fixed to the saddle memberat the intersection of the angulated extending arms 22a and 22b,respectively.

Alignment of each stiffener assembly 10 is in an ent-to-endrelationship, which is accomplished by guide means 40 attached to one ofthe brace members at its lower end. This guide means receives theadjacent brace member of the adjoining stiffener assembly. The guidemeans comprises two flat oppositely disposed fingers 42 which are fixedto each side of the end brace members, forming a substantially U-shapedconfiguration that can be clearly seen in FIG. 8. Said flat members orfingers 42 are welded to the surfaces of the brace member and are soarranged as to be located atone end of the stiffener structure 10. This,then, leaves the opposite end of the structure free to engage in theguide members of an adjoining structure. Not only is guide means 40 usedto control lateral movement of each adjoining stiffener structure, butit is used to keep the pressure pad faces 44 and 45 aligned for movableengagement with each other. It can be seen, as illustrated in FIG. 3,that any stress which is placed upon stringer 12 would cause a downwardbending moment whereby faces 44 and 45 would be brought into contactwith each other. This, then, would limit any further bending to occur inthe string of pipe. Thus, the pipe is protected from undue damage bylimiting the bending stress before it reaches the yield point.

Referring now to FIG. 6, there is shown a main stringer pipe 12supporting a typical type bundle, indicated at 46. Generally, thestringer pipe is the largest and the most rigid pipe of the group,normally having a diameter of 8 inches or better. The attached bundle ofpipes typically comprises a variety of pipe sizes having diameters of 2to 4 inches and are secured to the structure stringer pipe 12 in a groupby any suitable means but, for illustrative purposes, it has been showntied down by a strap or a band 48. These pipes can be used in varyingnumbers and sizes depending upon the requirements of any one givensituation.

At this time, the other configurations and uses of underwater stiffenerstructures should be also considered.

If stiffeners are required at a point far from the connectors at eachend, the pipe could possibly be twisted so that the center plane of thestiffener would not coincide with the plane of the bending moment. Therewill occasionally occur a situation wherein the pipe and/or pipe bundleis of such length along the ocean floor that it is subjected to unduetwisting about itself. Thus, a bend in the pipe would then becomeunstable. In this case, a configuration, as shown in FIG. 9, should beused. The pipe then would become stable for any bending plane as long asit stays between the center lines of the stiffener 50 and 52,respectively. The bundle of pipe, generally indicated at 46, as well aspipe stringer 12 are supported by the stiffeners 50 and 52,respectively. Each of the stiffeners are attached to the stringer pipein the same manner as hereinbefore described. However, the positioningof the structures are such that they are not only in end-to-cndrelationship but are, in addition, placed side by side at right anglesto each other. The right angle relationship is indicated at A whichcomprises an angle of approximately Thus, the arrangement will resistbending moments in a plane that would be subjected to more than arotation of plus or minus 45, on each side of the center thereof.

Another configuration is illustrated in FIG. wherein the pipe will besubjected to a condition having a positive or negative bending moment.This condition is apt to occur where the pipe would have a tendency todevelop a double bend at crossings such as ravines or crevices. Thissituation is most likely to be brought about at a point along the pipe,as indicated at 10-10 in FIG. 1. Here again, the attachment of thestiffener structures are accomplished as hereinbefore described, withthe exception that each stiffener assembly 10 is positioneddiametrically opposite the other, that is, each being separated from theother by half the circumference of the pipe 12.

We claim:

1. A stiffening assembly for elongated pipe comprising:

a rigid skeletal structure having a support beam angulated at itsmidportion;

a brace connected to each end of the support beam and extendingsubstantially perpendicular thereto;

a column member connected at its respective ends to the ends of eachrespective braces remote from said support beam; and

means for maintaining said support beam in fixed position along thelength of said elongated pipe.

2. A stiffening assembly as recited in Claim 1 including:

a guide means attached to one of said braces at the end thereof remotefrom said support beam for receiving a brace ofa second similaradjoining stiffener assembly.

3. A structural stiffening assembly for an elongated element which issubjected to a limited amount of bending, said assembly comprising:

a plurality of stiffener structures adapted to be secured to saidelongated element in end-to-end relationship to each other, each of saidstructures comprising:

a support beam having an apex, said beam being divergently angulatedfrom said apex;

a securing means for securing said support beam to said elongatedelement;

a brace connected to each end of said support beam and extendingsubstantially perpendicular thereto;

a slidable guide means fixed to one brace of each structure and adaptedto receive an adjoining brace of the adjacent structure; and

a column connected at its respective ends to the free ends of saidrespective braces and remote from said support beam.

4. An assembly as recited in claim 3 wherein said securing meanscomprises:

a saddle member positioned at the apex of said support beam forreceiving said elongated element; and

a connecting means for connecting said saddle to said elongated elementwhereby said stiffener structures may be secured in end-to-endrelationship to each other in predetermined positions along the lengthof said elongated element.

5. An assembly as recited in claim 4 wherein said stiffener structureincludes:'

a shoe mounted to each opposite end of said support beam, said shoeformed to receive said elongated element for engagement therewith, whensaid element has a bending moment in the direction of said shoe.

6. An assembly as recited in claim 5 wherein said stiffener structureincludes:

a guide means for positioning an adjacent stiffener in endto-endalignment, said guide means fixed to one of said braces of the lower endthereof.

7. An assembly as recited in claim 6 wherein said stiffener structurefurther includes:

a center brace support joined at one end to said support beam at theapex thereof, and the opposite end joined to said column intermediatethe ends thereof; and a pair of diagonal supporting truss, each of saidtruss having one end fixed to said column and the opposite end thereofis fixed to said saddle member adjacent to said support beam.

8. A structural stiffening assembly for support of an elongated elementwhich is subjected to a limited amount of bending comprising:

a plurality of stiffener structures adapted to be secured to saidelongated element in end-to-end relations, each said structurecomprising:

a nonlinear convexed support beam having free ends thereon;

securing means for securing said stiffener structure to said elongatedelement, said means being positioned intermediate the free ends of saidsupport beam;

a pair of end braces each connected to each free end of said supportbeams and extending perpendicular thereto, and in spaced relationshipwith an adjoining end brace of the adjacent stiffener structure; and atruss arrangement interposed between said end braces and attachedthereto.

9. A structural assembly as recited in claim 8 including:

a guide means for end-to-end alignment with adjacent stiffener assembly,said guide means attached to one of said braces at the end thereof,remote from said support beam for receiving a brace of said adjoiningstiffener assembly.

10. A structural stiffening assembly for support of elongated pipeelement comprising: a first group of stiffeners attached to saidelongated pipe element in end-to-end relationship to each other; and asecond group of stiffeners attached to said elongated pipe element inend-to-end relationship with each other, and positioned adjacent and atright angles to said first group of stiffeners, whereby said elongatedelement becomes stable, wherein each of said stiffeners comprises arigid skeletal structure having a support beam angulated at itsmidpoint;

a brace connected to each end of the support beam and extendingsubstantially perpendicular thereto;

a column member connected at its respective end to the ends of eachrespective braces remote from said support beam;

means for maintaining said support beam in fixed position along thelength of said elongated pipe element; and

a guide means attached to one of said braces at the end thereof, remotefrom said support beam for receiving a brace of a second similaradjoining stifi'ener assembly.

11. A structural stiffening assembly for support of an elongated pipeelement having a positive and negative bending moment comprising: afirst group of stifieners attached to said elongated pipe element inend-to-end relationship to each other; and a second group of stiffenersattached to said elongated pipe element in end-to-end relationship witheach other, and positioned diametrically opposite said first group, eachgroup being separated from the other by half the circumference of saidpipe element, wherein each of said stiffeners comprises:

a rigid skeletal structure having a support beam angulated at itsmidpoint;

a brace connected to each end of the support beam and extendingsubstantially perpendicular thereto;

a column member connected at is respective end to the ends of eachrespective braces remote from said support beam;

means for maintaining said support beam in fixed position along thelength of said elongated pipe element; and

a guide means attached to one of said braces at the end thereof, remotefrom said support beam for receiving a brace of a second similaradjoining stiffener assembly.

1. A stiffening assembly for elongated pipe comprising: a rigid skeletalstructure having a support beam angulated at its midportion; a braceconnected to each end of the support beam and extending substantiallyperpendicular thereto; a column member connected at its respective endsto the ends of each respective braces remote from said support beam; andmeans for maintaining said support beam in fixed position along thelength of said elongated pipe.
 2. A stiffening assembly as recited inClaim 1 including: a guide means attached to one of said braces at theend thereof remote from said support beam for receiving a brace of asecond similar adjoining stiffener assembly.
 3. A structural stiffeningassembly for an elongated element which is subjected to a limited amountof bending, said assembly comprising: a plurality of stiffenerstructures adapted to be secured to said elongated element in end-to-endrelationship to each other, each of said structures comprising: asupport beam having an apex, said beam being divergently angulated fromsaid apex; a securing means for securing said support beam to saidelongated element; a brace connected to each end of said support beamand extending substantially perpendicular thereto; a slidable guidemeans fixed to one brace of each structure and adapted to receive anadjoining brace of the adJacent structure; and a column connected at itsrespective ends to the free ends of said respective braces and remotefrom said support beam.
 4. An assembly as recited in claim 3 whereinsaid securing means comprises: a saddle member positioned at the apex ofsaid support beam for receiving said elongated element; and a connectingmeans for connecting said saddle to said elongated element whereby saidstiffener structures may be secured in end-to-end relationship to eachother in predetermined positions along the length of said elongatedelement.
 5. An assembly as recited in claim 4 wherein said stiffenerstructure includes: a shoe mounted to each opposite end of said supportbeam, said shoe formed to receive said elongated element for engagementtherewith, when said element has a bending moment in the direction ofsaid shoe.
 6. An assembly as recited in claim 5 wherein said stiffenerstructure includes: a guide means for positioning an adjacent stiffenerin end-to-end alignment, said guide means fixed to one of said braces ofthe lower end thereof.
 7. An assembly as recited in claim 6 wherein saidstiffener structure further includes: a center brace support joined atone end to said support beam at the apex thereof, and the opposite endjoined to said column intermediate the ends thereof; and a pair ofdiagonal supporting truss, each of said truss having one end fixed tosaid column and the opposite end thereof is fixed to said saddle memberadjacent to said support beam.
 8. A structural stiffening assembly forsupport of an elongated element which is subjected to a limited amountof bending comprising: a plurality of stiffener structures adapted to besecured to said elongated element in end-to-end relations, each saidstructure comprising: a nonlinear convexed support beam having free endsthereon; securing means for securing said stiffener structure to saidelongated element, said means being positioned intermediate the freeends of said support beam; a pair of end braces each connected to eachfree end of said support beams and extending perpendicular thereto, andin spaced relationship with an adjoining end brace of the adjacentstiffener structure; and a truss arrangement interposed between said endbraces and attached thereto.
 9. A structural assembly as recited inclaim 8 including: a guide means for end-to-end alignment with adjacentstiffener assembly, said guide means attached to one of said braces atthe end thereof, remote from said support beam for receiving a brace ofsaid adjoining stiffener assembly.
 10. A structural stiffening assemblyfor support of elongated pipe element comprising: a first group ofstiffeners attached to said elongated pipe element in end-to-endrelationship to each other; and a second group of stiffeners attached tosaid elongated pipe element in end-to-end relationship with each other,and positioned adjacent and at right angles to said first group ofstiffeners, whereby said elongated element becomes stable, wherein eachof said stiffeners comprises a rigid skeletal structure having a supportbeam angulated at its midpoint; a brace connected to each end of thesupport beam and extending substantially perpendicular thereto; a columnmember connected at its respective end to the ends of each respectivebraces remote from said support beam; means for maintaining said supportbeam in fixed position along the length of said elongated pipe element;and a guide means attached to one of said braces at the end thereof,remote from said support beam for receiving a brace of a second similaradjoining stiffener assembly.
 11. A structural stiffening assembly forsupport of an elongated pipe element having a positive and negativebending moment comprising: a first group of stiffeners attached to saidelongated pipe element in end-to-end relationship to each other; and asecond group of stiffeners attached to said elongated piPe element inend-to-end relationship with each other, and positioned diametricallyopposite said first group, each group being separated from the other byhalf the circumference of said pipe element, wherein each of saidstiffeners comprises: a rigid skeletal structure having a support beamangulated at its midpoint; a brace connected to each end of the supportbeam and extending substantially perpendicular thereto; a column memberconnected at is respective end to the ends of each respective bracesremote from said support beam; means for maintaining said support beamin fixed position along the length of said elongated pipe element; and aguide means attached to one of said braces at the end thereof, remotefrom said support beam for receiving a brace of a second similaradjoining stiffener assembly.